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Origin of optical pleochroism in orthopyroxenes

Published online by Cambridge University Press:  14 March 2018

Roger G. Burns
Roger G. Burns*
Affiliation:
Department of Mineralogy and Petrology, University of Cambridge, Cambridge
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Summary

The necessary conditions for optical pleochroism in orthopyroxenes are: ordering of Fe2+ ions, with preferential occupation of M2 positions; presence of small, high-valence cations (Al3+, Fe3+, Ti4+) in M1 positions; replacement of Si by Al; and a sufficient Fe2+ content. These factors favour an intensification of the charge-transfer absorption bands in the ultra-violet that is more marked for the α vibration direction than for β and γ. This leads to absorption in the blue and a red colour in transmitted α-polarized light, while β and γ, remain green.

Type
Research Article
Information
Mineralogical magazine and journal of the Mineralogical Society , Volume 35 , Issue 273 , March 1966 , pp. 715 - 719
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1966

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References

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